Method for producing a fabric with close setting of the weft threads



0. GRIMM Aug. 2, 1938.

METHOD FOR PRODUCING A FABRIC WITH CLOSE SETTING OF THE WEFT THREADS Filed Jan. 14, 1935 Patented Aug. 2, 1938 PATENT OFFICE METHOO FOR PRODUCING A FABRIC WITH CLOSE SETTING OF THE WEFT THREADS Oskar Grimm, Lengenfeld, Germany Application January 14, 1935, Serial No. 1,830 In Germany January 16, 1934 3 Claims.

It is known when weaving a fabric to subdivide the warp threads and to bring them under irregular tension during the beating up so as to cause the warp threads to slide on the weft threads last picked and to obtain thereby a uniform distribution of the warp threads in the fabric. Back rests are employed which can be adjusted only in dependency upon one another. Their operation is such that alternately at every blow of the slay one half of the warp is stretched and in dependency thereon the other half slackened to a corresponding extent. The irregular tension thus produced-between the warp halves certainly allows the weft threads last picked to yield towards the upper or lower side of the fabric during the blow of the slay, but the change of tension positively following during the passing of the shuttle and extending over the entire shed forming and the whole of the slay movement causes the immediate return of the weft threads into the warp plane while the warp threads are not secured. The primary conditions for obtaining increased web density are lost, because the slackened warp portions are always again positively stretched during the passage of the shuttle and prematurely withdrawn from the fabric.

The object of the invention is, to retard for a period of several blows the return into the warp plane of the weft threads pressed towards the upper or lower side of thefabric during the blow of the reed, and with the aid of this retarded return of the weft threads into the plane of the warp to produce a fabric with very dense weft. This is attained according to the invention by subdividing the warp threads into groups corresponding to the number of healds and by influencing the individual groups as regards tension by means of back-rests periodically swinging independently of one another in such a manner that during the beating up of the weft'thread last picked slips over or under the previously picked weft thread. This position of the weft thread is ensured by changing the tension between the individual groups of warp threads only when the weft thread last picked is prevented by the loom slay which is in the beating up position from yielding back into the warp plane. The change of tension between the individual groups of warp threads is confined to a very short period during the beating up period. This short change in tension in the groups of warp threads, independently of one another and at different velocities, shortly before, during, and shortly after the dead centre position of the loom slay and their alternating relative positions during the beating up period causes the last picked weft threads to preserve the position assumed during theblow for a period of several blows, that is to remain loosely on the fabric outside the warp plane and on-y successively bind tightly in the fabric in dose setting owing to the change of tension between the groups of warp threads being transmitted to these weft threads. The slackening of the individual groups of warp threads can take place several times successively in each group, provided there is a sufficient length of warp threads in this group. A change in the tensional condition between the groups of warp threads must only take place when this warp thread length is used up.

The changes in the tension conditions of the individual groups of Warp threads for a plan weave and a twill are shown by way of example in their simplest forms in the accompanying drawing in which:

Figs. 1 and 2 illustrate diagrammatically the arrangement of a subdivided warp on two independently movable back rests, their alternating relative positions during the blows of the slay for a fabric with two ends and their action upon the weft threads.

Figs. 3 to 5 show similar views for a fabric with three ends.

According to Figs. 1 and 2 the .warp a, during the running off of the warp beam, is divided into two groups b, c, which are each conducted over one of the back rests d, e and taken up by healds I and 2 respectively. The operation is as follows:

If, according to Fig. 1, a weft thread is beaten up, the back rest e is in an inwardly inclined position and slackens the warp thread group 6, whereas at the same time the backrest d is in outwardly inclined position and holds the warp thread group b under tension. Owing to the unequal tension present in the warp thread groups b and c, the weft thread lies over or under the fabric. Whilst the loom slay swings back, the change of shed takes place and the next weft thread is picked into the shed, the warp thread group c remains slackened, irrespectively of the warp thread group b until the loom slay approaches its next blow. Shortly before the blow, the change in the tension conditions between the two groups of warp threads takes place. The back rests precipitately move into the position shown in Fig. 2. The back rest d is inwardly inclined and slackens the warp thread group b, whereas at the same time the back rest e is outwardly inclined and stretches the warp thread group 0. W i

The warp thread group I) this slackens to such an extent that it allows the weft threads to yield towards the npper and lower side of the fabric. However, irrespectively thereof the tension of the warp thread group c also increases so rapidly thatan effective transmission of tension to the weft threads lying in the fabric takes place, whereas they are held by the loom slay in its beating up position. The we back rests remain in this position until'the next following beating up period begins and only then return into the positions illustrated Fig. l.

The oscillating movements of the back rests illustrated in Figs. 1 and 2': can be regulated in such a manner that they preserve the position shown in Fig. 1 for the 1st and 2nd weft thread beating up operation and only then assume the position shown in Figs. 3 and 4 for the 3rd and 4th weft thread beating up operations. The swinging movement-s may also be subdivided so that, for example, the back rest e is only half swung inwards for the beating up of the 1st weft thread and only assumes the position illustrated in Fig. 1 for the beating up of the 2nd .weft thread (the back rest d remaining still the while or carrying out a limited stretching movement), whereas the-back rest d in the proper succession then swings only half inwards for the beating up of the third weft thread and only assumes the position shown in Fig. 2 for the heating up of the 4th weft thread (the back rest e remaining still the while or carrying out a limited stretching movement).

The slackening of the individual warp thread groups can therefore be carried out in successive stages in each group provided there is a sufflcient length of warp thread for feeding. The tension conditions must, however, be changed when the length of warp thread is used up. .It must take place rapidly when the weft thread last beaten up is prevented from yielding by the slay being in its beating position, so that the change of tension is transmitted to the weft threads lying loosely on the edge of the fabric and, as shown diagrammatically in Figs. 1 and 2, successively binds them tightly in the fabric inclosely set order.

' The subdividing of the warp threads and the number of back rests depends upon the number of healds necessary for the fabric to be produced.

In the arrangement of three groups of warp threads according to Figs. 3 to 5 the threads of theindividual groups are separately conducted over independently movable back rests l+, 2+, 3+ to the healds I, 2 and 3 respectively. Fig. 3 shows the position of the back rests and their actic n on the individual groups of warp threads for the beating upof the 1st weft thread, Figs. 4 and 5 showing the changed positiens for the beating up of the 2nd and 3rd weft threads.

Owing to the different mutual positions of the back rests the tehsion condition between t e warp thread groups is such that there is alw ys a tau a "slackened and a loose group of warp threads. Each of the three groups passes through these three stages, they being for example slack in the upper shed, pass into the lower shed in loosened condition for the following beating up operation of the weft thread and are then drawn tautfor the next following beating up operation of the weft thread. Consequently, whilst there is a slackened warp thread group for example in the upper shed, a loose group of warp threads and a taut group of warp threads are in the lower shed.

Thefalteration in the tension conditions between the groups of threads takes place when the last picked weft threads are prevented from yielding by the loom slay situated in its beating up position.

I claim:-

1. A method for producing a fabric with very densely picked weft, consisting in dividing the warp threads into a number of groups corresponding to the number of healds, and in alternately siackening and tightening onegroup as the other is alternately tightened and slackened at successive blows of the slay.

2. A method as specified in claim 1, consisting in changing the tension conditions between the inthvidual groups of warp threads while the last picked weft thread is secured in the position it has assumed by the beating up and pushing, during the beating up, the last picked thread over and under respectively, the preceding weft thread.

3. A method as specified in claim 1, in which the changing of the tension conditions between the individual groups of warp threads is effected in stages.

OSKAR GRIMM. 

